Fero-magnetic fluid is the stuff that Ferrari makes its car suspensions from. It's a fluid containing iron particles. When an electromagnetic force is applied to it, it tends to shape itself to the wave lines of the electromagnetic field. You can try something similar at home with some iron shavings on a plate, and a magnet underneath the plate. It's used in car suspensions because it can modify the stiffness of the ride almost instantly.

Her's another use for fero-magnetic fluid, this time with beauty in mind, and less practical. Enjoy it!